Network element clocking accuracy and stability monitoring over a packet-switched network

Abstract

Various exemplary embodiments include a method and related system and monitoring entity including one or more of the following: generating timing information at a master node in a packet-switched network, the timing information specifying a value of a master clock; communicating the timing information from the master node to a plurality of slave nodes over a first plurality of time-division multiplexing (TDM) pseudowires; running a digital phase-locked loop on each slave node to synchronize each slave node to the master clock, wherein each digital phase-locked loop outputs a frequency at which the respective slave node is operating; sending the frequency outputted by each digital phase-locked loop to a monitoring entity over a second plurality of TDM pseudowires; utilizing the outputted frequencies at the monitoring entity to identify all slave nodes that are experiencing timing problems; and implementing a remedial measure for all slave nodes that are experiencing timing problems.

1. A method for monitoring timing outputs over a packet-switched network, the method comprising:
 generating timing information at a master node in the packet-switched network, the timing information specifying a value of a master clock; 
 communicating the timing information from the master node to a plurality of slave nodes; 
 running a digital phase-locked loop on each slave node to synchronize each slave node to the master clock, wherein each digital phase-locked loop outputs a frequency at which the respective slave node is operating; 
 sending the frequency outputted by each digital phase-locked loop to a monitoring entity over a second plurality of TDM pseudowires; 
 utilizing the outputted frequencies at the monitoring entity to identify all slave nodes that are experiencing timing problems; and 
 implementing a remedial measure for all slave nodes that are experiencing timing problems. 
 
     
     
       2. The method for monitoring timing outputs according to  claim 1 , wherein the monitoring entity is the master node or is of a network element type that is the same as a network element type of the master node. 
     
     
       3. The method for monitoring timing outputs according to  claim 1 , wherein the step of utilizing the outputted frequencies comprises the following sub-steps:
 inputting the outputted frequency for each slave node into one of a plurality of digital phase-locked loops running on the monitoring entity, wherein each loop corresponds to one of the plurality of slave nodes; 
 determining, for each of the plurality of digital phase-locked loops, a parameter used to adjust a digitally-controlled oscillator of each of the plurality of loops, wherein an input into each digitally-controlled oscillator is a common oscillator shared by each of the plurality of the loops; 
 analyzing each parameter to identify all parameters that are outside of an acceptable range; and 
 for each parameter outside of the acceptable range, identifying the slave node corresponding to the parameter as experiencing timing problems. 
 
     
     
       4. The method for monitoring timing outputs according to  claim 3 , further comprising:
 running a reference phase-locked loop that shares the common oscillator and receives, as input, a reference frequency known to be accurate; 
 setting a reference parameter equal to a value of a parameter used to adjust a digitally-controlled oscillator in the reference phase-locked loop, the digitally-controlled oscillator in the reference phase-locked loop receiving, as input, the common oscillator; and 
 comparing each parameter associated with a slave node to the reference parameter to identify all parameters that are outside of the acceptable range. 
 
     
     
       5. The method for monitoring timing outputs according to  claim 3 , wherein the sub-step of analyzing each parameter comprises:
 performing statistical analysis to identify all parameters that are statistical outliers using at least one of a mean of all parameters and a standard deviation for each parameter. 
 
     
     
       6. The method for monitoring timing outputs according to  claim 3 , wherein each parameter is an offset value used to adjust the frequency output of the digitally-controlled oscillator. 
     
     
       7. The method for monitoring timing outputs according to  claim 1 , wherein the remedial measure comprises:
 notifying a network operator of all slave nodes that are experiencing timing problems. 
 
     
     
       8. The method for monitoring timing outputs according to  claim 1 , wherein the remedial measure comprises:
 for each slave node that is experiencing timing problems, selecting a new master node from which the slave node should receive timing information. 
 
     
     
       9. A system for monitoring timing outputs for packet-based services, the system comprising:
 a master node in a packet-switched network, the master node comprising:
 a timing generation module that generates timing information specifying a value of a master clock, and 
 a transmitter that communicates the timing information to slave nodes; 
 
 a plurality of slave nodes in the packet-switched network, each slave node comprising:
 a digital phase-locked loop that synchronizes the slave node to the master clock, wherein the digital phase-locked loop outputs a frequency at which the slave node is operating, and 
 a transmitter that sends the frequency outputted by the digital phase-locked loop over a respective TDM pseudowire of a second plurality of TDM pseudowires; and 
 
 a monitoring entity in the packet-switched network, the monitoring entity comprising:
 a plurality of digital phase-locked loops that share a common oscillator, each of the plurality of loops corresponding to one of the plurality of slaves nodes and receiving the outputted frequency from the corresponding slave node, and 
 a statistical analysis module that receives a value from each of the plurality of digital phase-locked loops and processes each value to identify all slave nodes that are experiencing timing problems. 
 
 
     
     
       10. The system for monitoring timing outputs according to  claim 9 , wherein the master node and the monitoring entity are the same node. 
     
     
       11. The system for monitoring timing outputs according to  claim 9 , wherein:
 each of the plurality of digital phase-locked loops in the monitoring entity receives, as input, the outputted frequency from the corresponding slave node, 
 each of the plurality of digital phase-locked loops tunes an operating frequency of the loop to the outputted frequency from the corresponding slave node by adjusting a parameter associated a digitally-controlled oscillator, wherein each digitally-controlled oscillator receives, as input, the common oscillator, and 
 the statistical analysis module analyzes all parameters from the plurality of digital phase-locked loops to identify parameters that are outside of an acceptable range and, for each parameter outside of the acceptable range, identifies the slave node corresponding to the parameter as experiencing timing problems. 
 
     
     
       12. The system for monitoring timing outputs according to  claim 11 , wherein:
 each of the plurality of digital phase-locked loops in the monitoring entity further comprises a reference phase-locked loop that shares the common oscillator and receives, as input, a reference frequency known to be accurate, and 
 the statistical analysis module compares each parameter associated with a slave node to a reference parameter used to adjust a digitally-controlled oscillator in the reference phase-locked loop and thereby identifies all parameters associated with a slave node that are outside of an acceptable range. 
 
     
     
       13. The system for monitoring timing outputs according to  claim 11 , wherein the statistical analysis module considers at least one of a mean of all parameters and a standard deviation for each parameter. 
     
     
       14. The system for monitoring timing outputs according to  claim 11 , wherein each parameter is an offset value used to adjust the frequency output of the digitally-controlled oscillator. 
     
     
       15. The system for monitoring timing outputs according to  claim 9 , wherein the monitoring entity further comprises:
 a transmitter that sends an identification of all slave nodes that are experiencing timing problems to a network operator. 
 
     
     
       16. The system for monitoring timing outputs according to  claim 9 , wherein the monitoring entity further comprises:
 a transmitter that sends a message to each slave node that is experiencing timing problems, the message indicating that the slave node should select a new master node from which the slave node should receive timing information. 
 
     
     
       17. A monitoring entity for monitoring timing outputs exchanged between nodes in a packet-switched network, the monitoring entity comprising:
 a receiver configured to receive packets from a plurality of slave nodes, the packets specifying an operating frequency of each slave node, wherein each slave node sets the operating frequency using timing information received from a master node; 
 a plurality of digital phase-locked loops that share a common oscillator, with one loop corresponding to each slave node, wherein:
 each of the plurality of digital phase-locked loops receives, as input, the outputted frequency from the corresponding slave node, and 
 each of the plurality of digital phase-locked loops tunes an operating frequency of the loop to the outputted frequency from the corresponding slave node by adjusting a parameter associated with a digitally-controlled oscillator, wherein each digitally-controlled oscillator receives, as input, the common oscillator; and 
 
 a statistical analysis module that analyzes each parameter to identify all parameters that are outside of an acceptable range and, for each parameter outside of the acceptable range, identifies the slave node corresponding to the parameter as experiencing timing problems. 
 
     
     
       18. The monitoring entity for monitoring timing outputs according to  claim 17 , wherein:
 the plurality of digital phase-locked loops in the monitoring entity further comprises a reference phase-locked loop that shares the common oscillator and receives, as input, a reference frequency known to be accurate, and 
 the statistical analysis module compares each parameter associated with a slave node to a reference parameter used to adjust a digitally-controlled oscillator in the reference phase-locked loop and thereby identifies all parameters associated with a slave node that are outside of an acceptable range. 
 
     
     
       19. The monitoring entity for monitoring timing outputs according to  claim 17 , wherein each parameter is an offset value used to adjust the frequency output of the digitally-controlled oscillator. 
     
     
       20. The monitoring entity for monitoring timing outputs according to  claim 17 , wherein the statistical analysis module considers at least one of a mean of all parameters and a standard deviation for each parameter. 
     
     
       21. The monitoring entity for monitoring timing outputs according to  claim 17 , wherein the node further comprises:
 a transmitter that sends an identification of all slave nodes that are experiencing timing problems to a network operator. 
 
     
     
       22. The monitoring entity for monitoring timing outputs according to  claim 17 , wherein the node further comprises:
 a transmitter that sends a message to each slave node that is experiencing timing problems, the message indicating that the slave node should select a new master node from which the slave node should receive timing information.